J. Org. Chem. 1989,54, 2605-2608 mass spectrum, m / z (relative intensity) 290 (M', 25), 275 (7), 205 (281, 119 (loo), 91 (82); exact mass calcd for C19Hm02290.2247, found 290.2244. Ring-Cleavage Product 21. A ring-cleavage reaction was performed, starting from 157.8 mg (0.543 mmol) of 19, by a procedure similar to the one described above. Flash chromatography (20-25%) gave 191.2 mg (86%) of 21: oil; 'H NMR 6 0.84 (3 H, d, J = 6.4 Hz, CH3),0.89 (3 H, d, J = 6.0 Hz, CH,), 1.10-1.95 [13 H, m, including d (3 H, J = 6.4 Hz, CH3)at 1.151, 2.05-2.56 (4 H, m), 2.80 (1 H, br s), 2.93 (1H, d, J = 15.6 Hz, CH2COPh),2.93 (1H, br s), 3.04 (1H, m, CH20),3.36 (3 H, m, CH20),3.57 (1 H, d, J = 15.6 Hz, CH2COPh),6.09 (2 H, m, 2 CH=), 7.13 (3 H, m, Ar), 7.99 (2 H, m, Ar);IR (liquid film) 3560 (br) 1680 (s), 1020 (s), lo00 (s), 750 (s), 685 cm-' (e); mass spectrum, 410 (M',
